A Common Reference Material for Cadmium Isotope Studies – NIST SRM 3108     

Wafa Abouchami  Stephen J. G. Galer  Tristan J. Horner  Mark Rehkämper  Frank Wombacher  Zichen Xue  Myriam Lambelet  Melanie Gault‐Ringold  Claudine H. Stirling  Maria Schönbächler  Alyssa E. Shiel  Dominique Weis  Philip F. Holdship 《Geostandards and Geoanalytical Research》2013,37(1):5-17

Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio ¹¹⁴Cd/¹¹⁰Cd for NIST SRM 3108 lies within ～ 10 ppm Da^?1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use.  相似文献   

Cold seep communities in the deep eastern Mediterranean Sea: composition, symbiosis and spatial distribution on mud volcanoes   总被引：2，自引：0，他引：2  

Karine Olu-Le Roy  Myriam Sibuet  Aline Fiala-Mdioni  Serge Gofas  Carmen Salas  Andr Mariotti  Jean-Paul Foucher  John Woodside 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1915-1936

Two mud volcano fields were explored during the French–Dutch MEDINAUT cruise (1998) with the submersible NAUTILE, one south of Crete along the Mediteranean Ridge at about 2000 m depth (Olimpi mud field) and the other south of Turkey between 1700 and 2000 m depth (Anaximander mud field) where high methane concentrations were measured. Chemosynthetic communities were observed and sampled on six mud volcanoes and along a fault scarp. The communities were dominated by bivalves of particularly small size, belonging to families commonly found at seeps (Mytilidae, Vesicomyidae, Thyasiridae) and to Lucinidae mostly encountered in littoral sulfide-rich sediments and at the shallowest seeps. Siboglinid polychaetes including a large vestimentiferan Lamellibrachia sp. were also associated. At least four bivalve species and one siboglinid are associated with symbiotic chemoautotrophic bacteria, as evidenced by Transmission Electronic Microscopy and isotopic ratio measurements. Among the bivalves, a mytilid harbors both methanotrophic and sulfide-oxidizing bacteria. Video spatial analysis of the community distribution on three volcanoes shows that dense bivalve shell accumulations (mainly lucinids) spread over large areas, from 10% to 38% of the explored areas (2500–15000 m²) on the different volcanoes. Lamellibrachia sp. had different spatial distribution and variable density in the two mud volcano fields, apparently related with higher methane fluxes in the Anaximander volcanoes and maybe with the instability due to brines in the Olimpi area. The abundance and richness of the observed chemosynthetic fauna and the size of some of the species contrast with the poverty of the deep eastern Mediterranean. The presence of a specialized fauna, with some mollusk genera and species shared with other reduced environments of the Mediterranean, but not dominated by the large bivalves usually found at seeps, is discussed.  相似文献   

The macrozoobenthos of the Karavasta lagoon system (Albania): local assemblages and geographical comparisons     

Carlotta Nonnis Marzano  Maria Flavia Gravina  Alessandra Fianchini  Giuseppe Portacci  Myriam Gherardi  Angelo Tursi  Giuseppe Corriero 《Marine Ecology》2010,31(4):622-632

The macrozoobenthic assemblage from the Karavasta lagoon system, the main wetland of Albania, was studied on soft bottoms and artificial hard substrates. Three different communities were identified: the typical ‘brackish‐water community’, an ‘outlet community’ dominated by filter‐feeders, and a typical ‘marine community’, inhabiting fine sandy bottoms, where polychaetes are dominant, together with a few species of tunicates and bivalves, which colonize hard substrates. The occurrence of build‐ups of the bryozoan Conopeum seurati, settled on the upper portion of long submerged wooden poles, was the main feature of faunistic interest. The faunistic affinity between the zoobenthic assemblage recorded in the hyperhaline lagoon of Karavasta and the assemblages from two Italian lagoons, the brackish Lake of Lesina and the euhaline Lake of Fogliano, was considered according to the different hydrological conditions and the geographical location. Hydrological confinement and salinity were likely to be the leading factors influencing the benthic community composition in the Karavasta wetland area. Therefore, on a vaster spatial scale, the isolation and geographical proximity of the ecosystems and colonizing ability and dispersal changes of the species appear to be the main factors liable to produce faunal variations.  相似文献   

Bathymetric distribution patterns of Southern Ocean macrofaunal taxa: Bivalvia, Gastropoda, Isopoda and Polychaeta     

Angelika Brandt  Katrin Linse  Myriam Schüller   《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2013-2025

The aim of this study is to compare the depth distributions of four major Southern Ocean macrobenthic epi- and infaunal taxa, the Bivalvia, Gastropoda, Isopoda, and Polychaeta, from subtidal to abyssal depth. All literature data up to summer 2008, as well as the unpublished data from the most recent ANDEEP I–III (Antarctic benthic deep-sea biodiversity: colonisation history and recent community patterns) expeditions to the Southern Ocean deep sea are included in the analysis. Benthic invertebrates in the Southern Ocean are known for their wide bathymetric ranges. We analysed the distributions of four of the most abundant and species-rich taxa from intertidal to abyssal (5200 m) depths in depth zones of 100 m. The depth distributions of three macrofaunal classes (Bivalvia, Gastropoda, Polychaeta) and one order (Isopoda) showed distinct differences. In the case of bivalves, gastropods and polychaetes, the number of species per depth zone decreased from the shelf to the slope at around 1000 m depth and then showed stable low numbers. The isopods showed the opposite trend; they were less species rich in the upper 1000 m but increased in species numbers from the slope to bathyal and abyssal depths. Depth ranges of families of the studied taxa (Bivalvia: 31 families, Gastropoda: 60, Isopoda: 32, and Polychaeta: 46 families) were compiled and illustrated. At present vast areas of the deep sea in the Southern Ocean remain unexplored and species accumulation curves showed that only a fraction of the species have been discovered to date. We anticipate that further investigations will greatly increase the number of species known in the Southern Ocean deep sea.  相似文献   

Geophysical Study of the Valle Fértil Lineament Between 28°45′S and 31°30′S: Boundary Between the Cuyania and Pampia Terranes     

Antonio Introcaso  Myriam P. Martínez  Mario E. Gimnez  Francisco Ruiz 《Gondwana Research》2004,7(4):1117-1132

A gravimetric and magnetometric study was carried out in the north-eastern portion of the Cuyania terrane and adjacent Pampia terrane. Gravimetric models permitted to interpret the occurrence of dense materials at the suture zone between the latter terranes. Magnetometric models led to propose the existence of different susceptibilities on either side of the suture. The Curie temperature point depth, representing the lower boundary of the magnetised crust, was found to be located at 25 km, consistent with the lower limit of the brittle crust delineated by seismic data; this unusually thick portion of the crust is thought to release stress producing significant seismicity.

Moho depths determined from seismic studies near western Sierras Pampeanas are significantly greater than those obtained from gravimetric crustal models.

Considering mass and gravity changes originated by the flat-slab Nazca plate along Cuyania and western Pampia terranes, it is possible to reconcile Moho thickness obtained either by seismic or by gravity data. Thus, topography and crustal thickness are controlled not only by erosion and shortening but by upper mantle heterogeneities produced by: (a) the oceanic subducted Nazca plate with “normal slope” also including asthenospheric materials between both continental and oceanic lithospheres; (b) flat-slab subducted Nazca plate (as shown in this work) without significant asthenospheric materials between both lithospheres. These changes influence the relationship between topographic altitudes and crustal thickness in different ways, differing from the simple Airy system relationship and modifying the crustal scale shortening calculation. These changes are significantly enlarged in the study area. Future changes in Nazca Plate slope will produce changes in the isostatic balance.  相似文献   

Intraurban variability of PM10 and PM2.5 in an Eastern Mediterranean city     

Rawad Massoud  Alan.L Shihadeh  Mohamed Roumié  Myriam Youness  Jocelyne Gerard  Nada Saliba  Rita Zaarour  Maher Abboud  Wehbeh Farah  Najat Aoun Saliba 《Atmospheric Research》2011,101(4):893-901

The results of the first large scale chemical characterization of PM10 and PM2.5 at three different sites in the urban city of Beirut, Lebanon, are presented. Between May 2009 and April 2010 a total of 304 PM10 and PM2.5 samples were collected by sampling every sixth day at three different sites in Beirut. Observed mass concentrations varied between 19.7 and 521.2 μg m^? 3 for PM10 and between 8.4 and 72.2 μg m^? 3 for PM2.5, respectively. Inorganic concentrations accounted for 29.7–35.6 μg m^? 3 and 46.0–53.5 μg m^? 3 of the total mass of PM10 and PM2.5, respectively. Intra-city temporal and spatial variations were assessed based on the study of three factors: correlation coefficients (R) for PM and chemical components, coefficient of divergence (CODs), and source apportionment using positive matrix factorization (PMF). Based on R and COD of PM concentrations, the three sites appear homogeneous. However, when individual elements were compared, heterogeneity among sites was found. This latter was attributed to the variability in the percent contribution of biogenic and local anthropogenic source factors such as traffic related sources and dust resuspension. Other factors included the proximity to the Mediterranean sea, the population density and the topographical structure of the city. Hence, despite its small size (20.8 km²), one PM monitoring site does not reflect an accurate PM level in Beirut.  相似文献   

Identification of magnetic minerals related to hydrocarbon authigenesis in venezuelan oil fields using an alternative decomposition of isothermal remanence curves     

Milagrosa Aldana  Vincenzo Costanzo-Álvarez  Luis Gómez  Carlos González  Marisel Díaz  Pedro Silva  Myriam Rada 《Studia Geophysica et Geodaetica》2011,55(2):343-358

In this work we try to better characterise the shallow magnetic signature of hydrocarbon microseepage in oil fields from eastern and western Venezuela. To get a better insight of the processes involved, we attempt to find out the main magnetic phases responsible for the observed oil-related shallow magnetic anomalies. In this way, a new and alternative numerical approach to decompose Isothermal Remagnetization (IRM) curves is introduced. The method is based on a Direct Signal Analysis (DSA) of the IRM curve in order to identify the number and type of magnetic components. Representative wells from western (La Victoria) and eastern (San Joaquín) Venezuelan fields are studied. The DSA approach, together with rock magnetic experimental results, indicates that in the well from western Venezuela the main magnetic mineralogy associated to hydrocarbon microseepage is magnetite. Conversely, in the well from eastern Venezuela, these MS anomalies are mainly caused by the presence of Fe-sulphides (i.e. greigite). These results support the hypothesis of two different authigenic processes. For the well at the western field, we propose that a net electron transfer from the organic matter, degraded by hydrocarbon gas leakage, should occur precipitating Fe(II) magnetic minerals (e.g. magnetite). On the other hand, in the well of the eastern field, high concentrations of H2S at shallow levels, might allow the formation of secondary Fe-sulphides.  相似文献   

Determination of the 3D structure of an earthflow by geophysical methods: The case of Super Sauze, in the French southern Alps   总被引：2，自引：0，他引：2  

Myriam Schmutz  Roger Gurin  Pierre Andrieux  Olivier Maquaire 《Journal of Applied Geophysics》2009,68(4):500-507

In order to evaluate the risk associated by an earthflow to abruptly evolve into a torrential flow, the knowledge of its internal structure is necessary. Geotechnical methods are important to reach this goal. However, because of the rough topography associated with earthflows, their surface heterogeneities, and the spatial variations of the thickness of the potentially moving mass, non-intrusive geophysical methods offer a very useful tool that complements traditional geotechnical methods. We report the results of a comprehensive study covering a 150 m by 200 m area of the Super Sauze earthflow. This earthflow developed in black marls in the southern French Alps. Shallow electrical conductivity investigations, derived using low frequency domain electromagnetics, maps hidden gullies and crests and lateral variations of the clay and the water content within the first 5 m below the ground surface. Electrical resistivity tomography allows to extrapolate this information down to 10 m below the ground surface along selected transects. The vertical structure of the earthflow, down to the substratum, is defined precisely thanks to joint inversion of DC and TDEM vertical soundings along one profile: the flowing upper layer and the position of the substratum are clearly evidenced. Combining this geophysical datasets with geotechnical tests and drill holes, we provide an estimate of both the location and the volume of the potentially most dangerous areas of the earthflow.  相似文献   

Responses of benthic macrofauna and biogeochemical fluxes to various levels of mussel biodeposition: An in situ “benthocosm” experiment     

Myriam D. Callier  Marion Richard  Christopher W. McKindsey  Philippe Archambault 《Marine pollution bulletin》2009,58(10):1544-1553

An in situ experiment was done to evaluate the dose-dependent response of mussel biodeposition on benthic communities and biogeochemical fluxes. Natural benthic communities were exposed to 7 different levels of mussel biodeposition (equivalent to that produced by 0-764 mussels m⁻²) over 50 days. Benthic communities responded as predicted from the Pearson, T.H., Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanogr. Mar. Biol. Annu. Rev. 16, 229-311 model of organic enrichment. Total abundance and species richness decreased with increasing biodeposition. The abundance and biomass of opportunistic species (Capitella spp.) increased in the mesocosms subject to the greatest biodeposition. Sensitive species Tellina agilis and Pherusa plumosa tended to decrease in abundance and biomass with increasing biodeposition. The biotic index M-AMBI responded clearly to increased biodeposition and may be a useful tool for assessing the effect of mussel biodeposition on the benthic environment. These results are important for the construction of predictive models for determining environmental carrying capacity for bivalve aquaculture.  相似文献   

Influence of an oxygen minimum zone and macroalgal enrichment on benthic megafaunal community composition in a NE Pacific submarine canyon          下载免费PDF全文

Lia Domke  Myriam Lacharité  Anna Metaxas  Marjolaine Matabos 《Marine Ecology》2017,38(6)

Megafaunal diversity in the deep sea shows a parabolic pattern with depth. It can be affected by factors such as low oxygen concentration, which suppresses diversity, or the presence of submarine canyons, which enhances it. Barkley Canyon, located off the west coast of British Columbia, Canada, is a submarine canyon that extends from the continental margin (200 m) into the deep ocean (2,000 m). This canyon receives drift kelp from shoreline kelp forests and contains an oxygen minimum zone (OMZ) at 500 to 1,500 m depth. Our study investigated the abundance and diversity of epibenthic megafauna over a range of depths (200–2,000 m) and oxygen concentrations (0.5–5.0 ml/L) within Barkley Canyon, as well as changes in abundance near detrital kelp. Video was collected using the remotely operated vehicle ROPOS along seven 1‐km cross‐canyon (i.e., across the axis of the canyon) transects and three 40‐m perpendicular cross‐transects over kelp. Taxonomic groups were associated with depth, temperature, and the presence of pebbles. The OMZ restricted pennatulids, and edge effects along OMZ boundaries were observed for ophiuroids. The geomorphology of the sea floor affected the distribution of taxa across the canyon, with Porifera mainly found along the walls and Echinoidea within the canyon axis. Expected richness exhibited a bimodal pattern, peaking at 300 and 2,000 m, possibly due to the combined effect of the OMZ and the submarine canyon. Echinoidea aggregated near drift kelp at 200 and 300 m. We found that faunal communities in Barkley Canyon were influenced by several confounded factors including depth, oxygen and substrate. Understanding faunal patterns is paramount with increased exploitation and a changing climate.  相似文献